All cognition and behavior, from perception and memory to decision-making and action, requires the activation of specialized areas in the brain as well as the means to globally coordinate their activity in real time. Understanding how this coordination occurs both within the human brain and between human brains as in social interactions is vital to both basic and clinical neuroscience. The reason is that disruptions of coordinative interactions among cortical and subcortical areas and the breakdown of neural integration lie at the heart of major neuropsychiatric disorders such as schizophrenia and autism. The current research is aimed at understanding how regions of the human brain interact, couple and decouple during the course of behavior both in a single individual and between individuals. We employ a parametric approach in a set of well-defined experimental paradigms that allows us to investigate how coordinative interactions among brain regions flexibly reorganize and switch at critical values of a control parameter (a kind of spontaneous decision-making). The work will be carried out by a dedicated interdisciplinary team of researchers that includes cognitive neuroscientists, psychologists and physicists. It uses state-of-the-art brain imaging technology (e.g., fMRI, specially developed in house dual high density electrode arrays), behavioral methods and sophisticated computational analyses to uncover the neural circuitry, connectivity and mechanisms underlying behavioral coordination both within a single brain and between brains. The research questions emanate from the overarching theoretical framework of coordination dynamics which provides concepts, methods and tools to attack the outstanding question of how large scale integration in the brain and across brains is accomplished. We focus on two novel hypotheses: 1) that any coordinated human action engages two different, but overlapping neural systems, one tied to the stability of patterned behavior, and the other to modality-specific brain regions that represent the particular elements that comprise the behavioral pattern. We test this hypothesis by studying simple patterns of behavior that are known to differ in stability and how different combinations of sound, touch, vision and movement come together and split apart in time as coordination rate is varied; and 2) that similar within-brain networks underlie social (i.e., shared between-brain) neural representations in individuals engaged in social behavioral interactions. Elucidating the neural systems and mechanisms that subserve coordinated human behavior in an individual and in social interactions is the first step toward understanding disruptions of this coordination in neuropsychiatric disorders like autism and schizophrenia. [unreadable] [unreadable] [unreadable]